Method of manufacturing sputter targets with internal cooling channels

ABSTRACT

The present invention pertains to low temperature pressure consolidation methods which provide for bonding of target material ( 10 ) to the backing plate material ( 15 ) capable of withstanding the stresses imposed by high sputtering rates. The sputter target assemblies ( 5 ) in accordance with the present invention are preferably comprised of target materials ( 10 ) and backing plate materials ( 15 ) having dissimilar thermal expansion coefficients and incorporate internal cooling channels ( 20 ). In the preferred embodiment, the resulting bond and the formation of the cooling channels ( 20 ) are cooperative.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority filing benefit of (1) International PCT applicationPCT/US01/28411 filed Sep. 11, 2001, and published under PCT 21(2) in theEnglish language; (2) U.S. Provisional Application Ser. No. 60/231,917filed Sep. 11, 2000.

FIELD OF THE INVENTION

The present invention relates to sputter target assemblies for usewithin sputtering systems. More specifically, the present inventionpertains to sputter target assemblies with internal cooling channelswhich include a target material bonded, by low temperature pressureconsolidation, to a backing plate material.

BACKGROUND OF THE INVENTION

Cathodic sputtering is widely used for the deposition of thin films, orlayers, of material onto desired substrates. The sputtering processemploys gas ion bombardment of a target material having a face formed ofa material that is to be deposited as a thin film, or layer, on thegiven substrate. Ion bombardment of the target material not only causesatoms or molecules of the target material to be sputtered, it impartsconsiderable thermal energy to the sputter target assembly. This heat istypically dissipated by use of a cooling fluid circulated beneath,through or around a thermally conductive backing plate material that ispositioned in heat exchange relation with the target material.

The target material and backing plate material form a part of a cathodeassembly which, together with an anode, is placed in an evacuatedchamber that contains an inert gas, preferably argon. A high voltageelectrical field is applied across the cathode and anode. The inert gasis ionized by collision with the electrons ejected from the cathode.Positively charged gas ions are attracted to the cathode and, uponimpingement with the target material surface, dislodge the targetmaterial. The dislodged target material traverses the evacuatedenclosure and deposits, as a thin film, or layer, on the givensubstrate. The substrate is normally located proximate the anode withinthe evacuated chamber.

In addition to the use of an electrical field, increased sputteringrates have been achieved by concurrent use of an arch-shaped magneticfield that is superimposed over the electrical field and formed in aclosed loop configuration over the surface of the target. These methodsare known as magnetron sputtering methods. The arch-shaped magneticfield traps electrons in an annular region adjacent the target materialsurface thereby increasing the number of electron-gas atom collisions inthe annular region to produce an increase in the number of positivelycharged gas ions in the region that strike the target to dislodge thetarget material. Accordingly, the target material becomes eroded (i.e.,consumed for subsequent deposition on the substrate) in a generallyannular section of the target face, known as the target raceway.Magnetron sputtering imposes considerable thermal energy upon thesputter target assembly, especially within the concentrated annularregion of the target raceway.

In typical sputter target assemblies, the target material is attached toa nonmagnetic backing plate material. The backing plate material isnormally water-cooled to carry away the heat generated by the ionbombardment of the target material. In order to achieve good thermal andelectrical contact between the target material and backing platematerial, these members are commonly bonded to one another by means ofsoldering, brazing, diffusion bonding, clamping and by epoxy cement andthe like. These bonding methods typically involve imposition of hightemperatures. Sputter target assemblies bonded by these methods can bowor bend at high sputtering rates, especially when a large differenceexists between the coefficients of thermal expansion for the targetmaterial and backing plate material. In sputter target assemblies withinternal cooling channels, bowing and bending induces leakage; thetypical bonding methods, described above, tend to deform, or otherwisepartially constrict, the cooling channels. Additionally, known bondingtechniques, as discussed above, result in undesirable grain growth inthe target material or the resulting bond cannot withstand the stressesimposed by high sputtering rates.

Therefore, there remains a need in the art of sputter target assembliesfor a method of bonding the target material to the backing platematerial which will withstand the stresses imposed by high sputteringrates, will allow for use of materials with dissimilar thermal expansioncharacteristics, and will not induce grain growth or cooling channeldeformation.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide lowtemperature pressure consolidation methods, capable of withstanding thestresses imposed by high sputtering rates, for bonding target materialto backing plate material. The preferred sputter target assemblies inaccordance with the present invention are comprised of target materialsand backing plate materials and incorporate internal cooling channels.

The bonding methods of the present invention allow target and backingplate assembly bonding with the assembly exhibiting reduced bowing orbending. Additionally, the low temperature pressure consolidationmethods of the present invention do not cause undesirable grain growthof the target material or deformation of the cooling channels duringconsolidation of the target material with the backing plate material.

As a result, the sputter target assemblies in accordance with thepresent invention are able to utilize backing plate materials havinghigher thermal and lower electrical conductivity than the conventionalbacking plate materials normally compatible with a specific targetmaterial. The reduction of bowing and bending is especially beneficialin sputter target assemblies with internal cooling channels. Theopportunity for leakage is greatly reduced by use of the low temperaturepressure consolidation methods in accordance with the present invention.

A second objective of the present invention provides for formation ofthe cooling channels is such a way that the cooling channel formationalso results in an interference friction fit bond between the targetmaterial and the backing plate material. Thereby, the time and stepsnecessary for sputter target assembly production are greatly reduced.

Other advantages and benefits of the present invention will becomeapparent with further reference to the appended drawings, the followingdetailed description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a plan view of the preferred embodiment of the backingplate material, with grooves formed therein, for use in accordance withthe present invention;

FIG. 2 depicts a profile view of a section of the preferred backingplate material, taken along line 2—2 of FIG. 1, with grooves, coolantinlet and coolant outlet;

FIG. 3 depicts a plan view of a section of the preferred backing platematerial, taken along line 3 of FIG. 1, with coolant inlet and relatedpassageway;

FIG. 4 depicts a profile view of a section of the preferred backingplate material, taken along line 4 of FIG. 2, with coolant inlet andrelated passageway;

FIG. 5 depicts a profile view of the preferred sputter target assemblyin accordance with the present invention prior to consolidation of thetarget material and backing plate material;

FIG. 6 depicts a profile view of the preferred sputter target assemblyof FIG. 5 subsequent to consolidation of the target material and backingplate material;

FIG. 7 depicts a profile view of a second embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material and backing plate material;

FIG. 8 depicts a profile view of the second embodiment of the sputtertarget assembly of FIG. 7 subsequent to consolidation of the targetmaterial and backing plate material;

FIG. 9 depicts a profile view of a third embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material and backing plate material;

FIG. 10 depicts a profile view of the third embodiment of the sputtertarget assembly of FIG. 9 subsequent to consolidation of the targetmaterial and backing plate material;

FIG. 11 depicts a profile view of a fourth embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material and backing plate material;

FIG. 12 depicts a profile view of the fourth embodiment of the sputtertarget assembly of FIG. 11 subsequent to consolidation of the targetmaterial and backing plate material;

FIG. 13 depicts a profile view of a fifth embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material and backing plate material;

FIG. 14 depicts a profile view of the fifth embodiment of the sputtertarget assembly of FIG. 13 subsequent to consolidation of the targetmaterial and backing plate material;

FIG. 15 depicts a profile view of a sixth embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material and backing plate material;

FIG. 16 depicts a profile view of the sixth embodiment of the sputtertarget assembly of FIG. 15 subsequent to consolidation of the targetmaterial and backing plate material;

FIG. 17 depicts a profile view of a seventh embodiment of the sputtertarget assembly in accordance with the present invention prior toconsolidation of the target material, interposing material and backingplate material; and

FIG. 18 depicts a profile view of the seventh embodiment of the sputtertarget assembly of FIG. 17 subsequent to consolidation of the targetmaterial, interposing material and backing plate material.

DETAIL DESCRIPTION OF THE INVENTION

Referring initially to FIGS. 1-6, there is shown a preferred embodimentof a sputter target assembly 5 in accordance with the present invention.As best seen with reference to FIG. 6, the preferred sputter targetassembly 5 comprises a target material 10 bonded to a backing platematerial 15 such that cooling channels 20 are integrally formedtherewithin. Initially, both the target material 10 and the backingplate material 15 are formed into individual discs. In this preferredembodiment, grooves 30 (FIG. 5) are formed in the substantially circularmating surface 25 of the backing plate material 15. The grooves 30define a plurality of islands 32 where the mating surface 25 remains.Protruding portions 40, defining a mirror image of the grooves 30 ofmating surface 25, are formed in the substantially circular matingsurface 35 of the target material 10. As discussed in detail below, thegrooves 30 and the protruding portions 40 cooperate to result in afriction fit bond between the target material 10 and the backing platematerial 15, as well as, forming the cooling channels 20.

With specific reference to FIG. 5, the grooves 30 are shown to includeopposing sidewalls 45, 50, a bottom portion 55 and an opening 60. Eachsidewall 45,50 comprises an upper portion 65, 70, respectively, and alower portion 75, 80, respectively. The protruding portions 40 includeopposing sides 85, 90 and an end portion 95. Referring to FIG. 6, theprotruding portions 40 are shown as having been received within thegrooves 30 through openings 60. The upper portions 65, 70 of the grooves30 cooperate with the sides 85, 90 of the protruding portions 40 to forma friction fit bond between the target material 10 and the backing platematerial 15. Most preferably, the distance between the sides 85, 90 ofthe protruding portions 40, the “protruding portion thickness,” isgreater than the distance between the sidewalls 45, 50 of thecorresponding grooves 30, the “groove width.” When the protrudingportion thickness is greater than the groove width an “interferencefriction fit bond” results between the target material 10 and thebacking plate material 15 when the protruding portions 40 are receivedwithin the grooves 30.

Subsequent to forming the grooves 30 and protruding portions 40, themating surface 25 is positioned proximate mating surface 35, withprotruding portions 40 aligned with corresponding grooves 30, thesputter target assembly 5 is then bonded along an annular zone 100adjacent the peripheral boundary 105. This initial bonding along theannular zone 100 of the assembly 5 may be achieved by conventional meanssuch as by E-beam welding under vacuum conditions, TIG welding, and thelike. Preferably, the bonding of the peripheral boundary 105 of thetarget material 10 and backing plate material 15 is performed via E-beamwelding under vacuum conditions.

After the peripheral bonding, the sputter target assembly 5 isconsolidated, via pressure application thereto, at pressure of about 50tons-5,000 tons; preferably less than about 1,000 tons, under lowtemperature conditions preferably of about room temperature to about 38°C. The protruding portions 40 are friction fit, preferably interferencefriction fit, into the corresponding grooves 30 through openings 60. Thelocking joint of the invention can therefore be described as a frictionfit bond, preferably interference friction fit bond, formed between thesides 85, 90 of the protruding portions 40 and the corresponding upperportions 65, 70 of the grooves 30 sidewalls 45, 50. The artisan furtherwill appreciate that the peripheral bonding can occur after pressureconsolidation. Subsequent to consolidation, the mating surfaces 25, 30are in direct contact with one another and the protruding portions 40are received within grooves 30.

After the low temperature pressure consolidation, the sputter targetassembly 5 may be subjected to a low temperature annealing stepconducted at temperatures of about room to 400° C. for a period of 0.5to 4 hours. This will help ensure adequate adhesion of the pressureconsolidated surfaces.

The phrase “low temperature pressure consolidation” refers to pressureconsolidation that may occur at temperatures of less than about 50% ofthe melting temperature of the lower melting point of either the targetmaterial 10 or backing plate material 15. Preferably, this temperatureis less than about 200° C; most preferably at about room temperature upto about 38° C.

In the preferred embodiment, the lower portions 75, 80 and bottomportion 55 of the grooves 30 cooperate with the end portion 95 of theprotruding portions 40 to define the cooling channels 20. As can be seenin FIG. 6, the distance from the mating surface 25 to the bottom portion55 of the grooves 30, the “groove depth,” is greater than the distancefrom the mating surface 35 to the end portion 95 of the protrudingportions 40, the “protruding portion length.” The cross section of thecooling channels 20 can be increase, or decreased, by varying the groovewidth or by varying the differential in the groove depth with respect tothe protruding portion length.

With reference to FIGS. 1-4, the preferred backing plate material 15further includes a coolant inlet 110 and a coolant outlet 115. The inlet110 extends from the bottom side 120 of the backing plate material 15 toan inlet slot 125. The inlet slot 125 defines a passageway extendingfrom the inlet 110 to the cooling channels 20. The outlet 115 extendsfrom the bottom side 120 of the backing plate material 15 to an outletslot 130. The outlet slot 130 defines a passageway extending from thecooling channels 20 to the outlet 115.

Forming the grooves 30 in the target material 10 and the protrudingportions 40 in the backing plate is within the scope of the presentinvention. In either case, in the preferred embodiment, the grooves 30and protruding portions 40 cooperate to form the channels 20 and toprovide for an interference friction fit between the target material 10and the backing plate material 15.

The cooperation of the grooves 30 with the protruding portions 40 information of the cooling channels 20, while also resulting in aninterference friction fit bond between the target material 10 and thebacking plate material 15, is a significant improvement. The resultingdecrease in sputter target assembly 5 production time results in reducedcost.

A second embodiment of the present invention, depicted in FIGS. 7 and 8as element 205, incorporates the protruding portions 240 formed in thebacking plate material 215 along with the grooves 230. The grooves 230comprise opposing sidewalls 245, 250, a bottom portion 255 and anopening 260. The grooves 230 define a plurality of islands 232 where themating surface 225 remains. The protruding portions 240 extend from themating surface 25 of the islands 232 and form a substantial “M” shape incross section. As described in detail below, in this second embodiment,the bond between the target material 210 and the backing plate material215 results independent of the formation of the cooling channels 220;the grooves 230 and the protruding portions 240 do not mate with oneanother. The consolidation method associated with this second embodimentresults in cooling channels which can be made deeper than with use ofthe preferred embodiment for the same thickness of target material 210or backing plate material 215; this is due to the fact that theprotruding portions 240 do not occupy space in the grooves 230.

The sputter target assembly 205 is first bonded around an annular zone300 adjacent the periphery 305 of the target assembly 205. The initialbonding, along the peripheral border 305 of the assembly 205, may beachieved, as described with regard to the preferred embodiment, byconventional means.

Turning now to FIG. 8, there is shown a sputter target assembly 205, inaccordance with the second embodiment of the present invention,subsequent to the target material 210 and backing plate material 215being consolidated. The low temperature pressure consolidation method asdiscussed above with regard to the preferred embodiment is preferred. Asa result of the low temperature pressure consolidation the protrudingportions 240 penetrate into the target material 210 and disrupt theoxide film that may exist along the mating surface 235, thereby,promoting a metal to metal cold diffusion type bond. The tips 285, 290deform and fold back toward the mating surfaces 225, 235, providing aphysical locking mechanism, or “ZIP bond,” between the target material210 and backing plate material 215.

With further reference to FIG. 8, the deformed edges 286, 291 of the “M”shaped protruding portions 240 are bent toward the mating surfaces 225,235 as a result of the low temperature pressure consolidation. Each edge286, 291 forms a re-entrant angle of about 55-60° relative to the matingsurfaces 225, 235. Due to bending of the edges 286, 291, the tips 285,290 of the protruding portions 240 adjacent edges 286, 291. The ZIP bondtraps target material 246, 251 against separation forces, or vectors,that would act in shear or in a perpendicular direction relative to themating surfaces 225, 235. Thereby, a tenacious bond is formed betweenthe target material 210 and backing plate material 215. The assemblymethod of this second embodiment has shown promise in bondinghigh-purity target materials, such as Al, Al—Cu, or Al—Cu—Si, tolower-purity backing plate materials, such as Al 6061. The method mayalso be employed to bond Cu targets and Cu containing alloy targets over6061 Al (or other Al alloys) or Cu metallurgies (Cu Alloys). Theprotruding portion length is varied to increase, or decrease, the bondstrength.

Additionally, other target materials including Ta, W, and Ti and theiralloys may be bonded to backing plates in accordance with the invention.

In this second embodiment, a portion of the mating surface 235cooperates with the sidewalls 245, 250 and the bottom portion 255 of thegrooves 230 to form the cooling channels 220; the openings 260 arethereby sealed. As can be seen in FIG. 8, the protruding portions 240are not received in the grooves 230, therefore, the resulting crosssection of the cooling channels 220 is only dependent upon the size ofthe grooves 230.

Turning now to FIGS. 9 and 10, there is shown a third embodiment of thepresent invention. As best seen in FIG. 9, the sputter target assembly405 incorporates target material 410 and backing plate material 415. Aswith the second embodiment described above, the bond between the targetmaterial 410 and the backing plate material 415 results independent ofthe formation of the cooling channels 420. Unlike either of thepreceding embodiments, this third embodiment incorporates receptacles496, formed in the target material 410, for receiving the protrudingportions 440. Each receptacle 496 has opposing sidewalls 497, 499 and anopening 498.

With further reference to FIG. 9, the protruding portions 440 extendingfrom mating surface 425, along with grooves 430, are formed in thebacking plate material 415. Each of the protruding portions 440 hasopposing sides 485, 490 and an end portion 495. Each of the grooves 430has opposing sidewalls 445, 450, a bottom portion 455 and an opening460. The grooves 430 define a plurality of islands 432 where the matingsurface 425 remains.

Subsequent to forming the receptacles 496, the grooves 430 and theprotruding portions 440, the mating surface 435 is positioned proximatethe mating surface 425 with the protruding portions 440 aligned with thereceptacles 496. The assembly 405 is initially bonded around theperiphery 505 of the annular zone 500. This initial bonding ispreferably performed as was described with regard to the precedingembodiments.

The assembly 405 is then subjected to low temperature pressureconsolidation as with the preceding embodiments. In this thirdembodiment, the protruding portions 440 are received within receptacles496 through openings 498. The sides 485, 490 of the protruding portions440 cooperate with the sidewalls 497, 499 of the receptacles 496,respectively, to result in a friction fit bond between the targetmaterial 410 and the backing plate material 415.

With further reference to FIG. 10, it can be seen that a portion of themating surface 425 cooperates with the sidewalls 445, 450 and bottomportion 455 of the grooves 430 to form the cooling channels 420. Theopening 460 is thereby sealed.

The low temperature annealing step, as described above in regard to thepreferred embodiment, will induce improved bonding. As with thepreferred embodiment, it is preferable to employ a protruding portionthickness greater than the groove width, thereby, providing for aninterference friction fit between the target material 410 and thebacking plate material 415.

In addition to providing the ability to maximize the cooling channeldepth for a given target material 410 or backing plate material 415, asin regard to the second embodiment, this third embodiment furtherprovides the ability to maximize the protruding portion length. Thereby,the surface area associated with the friction fit bond is maximized.

Turning now to FIGS. 11 and 12, there is shown a fourth embodiment ofthe present invention. As best seen in FIG. 11, the sputter targetassembly 605 incorporates target material 610 and backing plate material615. As with the second and third embodiments described above, the bondbetween the target material 610 and the backing plate material 615results independent of the formation of the cooling channels 620. Thisfourth embodiment incorporates receptacles 696 along with grooves 630,formed in the backing plate material 615. Each of the grooves 630 hasopposing sidewalls 645, 650, a bottom portion 655 and an opening 660.The grooves 630 define a plurality of islands 632 where the matingsurface 625 remains. Similar to the third embodiment, the receptacles696 are for receiving the protruding portions 640. Each receptacle 696has opposing sidewalls 697, 699 and an opening 698. Unlike the thirdembodiment, the receptacles 696 are sloped in relation to the matingsurface 625, as apposed to being perpendicular to surface 625.

With further reference to FIG. 11, the protruding portions 640 extendingfrom mating surface 635 are formed in the target material 610. Each ofthe protruding portions 640 has opposing sides 685, 690 and an endportion 695.

Subsequent to forming the receptacles 696, the grooves 630 and theprotruding portions 640, the mating surface 635 is positioned proximatethe mating surface 625 with the protruding portions 640 aligned with thereceptacles 696. The assembly 605 is initially bonded around theperiphery 705 of the annular zone 700. This initial bonding ispreferably performed as was described with regard to the precedingembodiments.

The assembly 605 is then subjected to low temperature pressureconsolidation as with the preceding embodiments. In this fourthembodiment, the protruding portions 640 are received within receptacles696 through openings 698. The sides 685, 690 of the protruding portions640 cooperate with the sidewalls 697, 699 of the receptacles 696,respectively, to result in a friction fit bond between the targetmaterial 610 and the backing plate material 615. Additionally, theprotruding portions 640, when received in receptacles 696, trap thetarget material 646 against separation forces, or vectors, that wouldact in shear or in a perpendicular direction relative to the matingsurfaces 625, 635. Thereby, a tenacious bond is formed between thetarget material 610 and the backing plate material 615 combining thestrengths of the interference friction fit bond and the ZIP bond fromthe second and third embodiments.

With further reference to FIG. 12, it can be seen that a portion of themating surface 625 cooperates with the sidewalls 645, 650 and bottomportion 655 of the grooves 630 to form the cooling channels 620. Theopenings 660 are thereby sealed.

The low temperature annealing step, as described above in regard to thepreferred embodiment, will induce improved bonding. As with thepreferred embodiment, it is preferable to employ a protruding portionthickness greater than the groove width, thereby, providing for aninterference friction fit between the target material 610 and thebacking plate material 615.

In addition to providing the ability to maximize the cooling channel 620depth for a given target material 610 or backing plate material 615, asin regard to the second embodiment, and providing the ability tomaximize the protruding portion length as in the third embodiment, thisfourth embodiment further provides the ZIP bond feature of the secondembodiment.

Turning now to FIGS. 13 and 14, there is shown a fifth embodiment of thepresent invention. As best seen in FIG. 13, the sputter target assembly805 incorporates target material 810 and backing plate material 815. Aswith the second, third and fourth embodiments described above, the bondbetween the target material 810 and the backing plate material 815results independent of the formation of the cooling channels 820. Thisfifth embodiment incorporates receptacles 896 along with grooves 830,formed in the backing plate material 815. Each of the grooves 830 hasopposing sidewalls 845, 850, a bottom portion 855 and an opening 860.The grooves 830 define a plurality of islands 832 where the matingsurface 825 remains. Similar to the third and fourth embodiments, thereceptacles 896 are for receiving the protruding portions 840. Eachreceptacle 896 has opposing sidewalls 897, 899 and an opening 898.Similar to the fourth embodiment, the receptacles 896 are sloped inrelation to the mating surface 825, as apposed to being perpendicular tosurface 825. Unlike the fourth embodiment, the receptacles 896 areprovided in pairs, with each individual receptacle 896 of a given pairof receptacles 896 slopes in an opposite direction originating frommating surface 825.

With further reference to FIG. 13, the protruding portions 840 extendingfrom mating surface 835 are formed in the target material 810. Each ofthe protruding portions 840 has opposing sides 885, 890 and an endportion 895.

Subsequent to forming the receptacles 896, the grooves 830 and theprotruding portions 840, the mating surface 835 is positioned proximatethe mating surface 825 with the protruding portions 840 aligned with thereceptacles 896. The assembly 805 is initially bonded around theperiphery 905 of the annular zone 900. This initial bonding ispreferably performed as was described with regard to the precedingembodiments.

The assembly 805 is then subjected to low temperature pressureconsolidation as with the preceding embodiments. In this fifthembodiment, the protruding portions 840 are received within receptacles896 through openings 898. The sides 885, 890 of the protruding portions840 cooperate with the sidewalls 897, 899 of the receptacles 896,respectively, to result in a friction fit bond, preferably aninterference friction fit bond, between the target material 810 and thebacking plate material 815. Additionally, the protruding portions 840,when received in receptacles 896, trap the target material 846 againstseparation forces, or vectors, that would act in shear or in aperpendicular direction relative to the mating surfaces 825, 835.Thereby, a tenacious bond is formed between the target material 810 andthe backing plate material 815 combining the strengths of theinterference friction fit bond and the ZIP bond similar to the fourthembodiment only with double the number of protruding portions 840 andreceptacles 896.

With further reference to FIG. 14, it can be seen that a portion of themating surface 825 cooperates with the sidewalls 845, 850 and bottomportion 855 of the grooves 830 to form the cooling channels 820. Theopenings 860 are thereby sealed.

The low temperature annealing step, as described above in regard to thepreferred embodiment, will induce improved bonding. As with thepreferred embodiment, it is preferable to employ a protruding portionthickness greater than the groove width, thereby, providing for aninterference friction fit between the target material 810 and thebacking plate material 815.

In addition to providing the ability to maximize the cooling channel 820depth for a given target material 810 or backing plate material 815, asin regard to the second embodiment, and providing the ability tomaximize the protruding portion length as in the third embodiment, andproviding the ZIP bond feature of the fourth embodiment, this fifthembodiment provides two protruding portions 840 and receptacles 896corresponding to each island 832.

Turning to FIGS. 15 and 16, there is shown a sixth embodiment of asputter target assembly 1005 in accordance with the present invention.As best seen with reference to FIG. 15, the preferred sputter targetassembly 1005 comprises a target material 1010 bonded to a backing platematerial 1015 such that cooling channels 1020 are integrally formedtherewithin similar to the preferred embodiment. Initially, both thetarget material 1010 and the backing plate material 1015 are formed intoindividual discs. In this sixth embodiment, similar to the preferredembodiment, the grooves 1030 are then formed in the substantiallycircular mating surface 1025 of the backing plate material 1015. Thegrooves 1030 define a plurality of islands 1032 where the mating surface1025 remains. Unlike the preferred embodiment, the grooves 1030 areformed at a slope in reference to the mating surface 1025, as apposed tobeing perpendicular to surface 1025. Protruding portions 1040, defininga mirror image of the grooves 1030 of mating surface 1025, are formed inthe substantially circular mating surface 1035 of the target material1010. As discussed in detail below, the grooves 1030 and the protrudingportions 1040 cooperate to result in a friction fit bond, preferably aninterference friction fit bond, between the target material 1010 and thebacking plate material 1015, as well as, forming the cooling channels1020.

With specific reference to FIG. 15, the grooves 1030 are shown toinclude opposing sidewalls 1045, 1050, a bottom portion 1055 and anopening 1060. Each sidewall 1045, 1050 comprises an upper portion 1065,1070, respectively, and a lower portion 1075, 1080, respectively. Theprotruding portions 1040 include opposing sides 1085, 1090 and an endportion 1095. Referring to FIG. 16, the protruding portions 1040 areshown as having been received within the grooves 1030 through openings1060. The upper portions 1065, 1070 of the grooves 1030 cooperate withthe sides 1085, 1090 of the protruding portions 1040 to form a frictionfit bond, preferably an interference friction fit bond, between thetarget material 1010 and the backing plate material 1015.

Subsequent to forming the grooves 1030 and protruding portions 1040, themating surface 1025 is positioned proximate mating surface 1035, withprotruding portions 1040 aligned with corresponding grooves 1030, thesputter target assembly 1005 is then bonded along an annular zone 1100adjacent the peripheral boundary 1105. This initial bonding along theannular zone 1100 of the assembly 1005 may be achieved by conventionalmeans as in the previous embodiments.

After the peripheral bonding, the sputter target assembly 1005 isconsolidated, via pressure application thereto, preferably as with theprevious embodiments. The protruding portions 1040 are friction fit,preferably interference friction fit, into the corresponding grooves1030 through openings 1060. The locking joint of the invention cantherefore be described as a friction fit bond, preferably interferencefriction fit bond, formed between the sides 1085, 1090 of the protrudingportions 1040 and the corresponding upper portions 1065, 1070 of thegrooves 1030 sidewalls 1045, 1050. Subsequent to consolidation, themating surfaces 1025, 1030 are in direct contact with one another andthe protruding portions 1040 are received within grooves 1030.

After the low temperature pressure consolidation, the sputter targetassembly 1005 may be subjected to a low temperature annealing as withthe previous embodiments. This will help ensure adequate adhesion of thepressure consolidated surfaces.

In this sixth embodiment, the lower portions 1075, 1080 and bottomportion 1055 of the grooves 1030 cooperate with the end portion 1095 ofthe protruding portions 1040 to define the cooling channels 1020. As canbe seen in FIG. 16, the distance from the mating surface 1025 to thebottom portion 1055 of the grooves 1030, the “groove depth,” is greaterthan the distance from the mating surface 1035 to the end portion 1095of the protruding portions 1040, the “protruding portion length.” Thecross section of the cooling channels 1020 can be increase, ordecreased, by varying the groove width or by varying the differential inthe groove depth with respect to the protruding portion length.

As with the preferred embodiment, the cooperation of the grooves 1030with the protruding portions 1040 in formation of the cooling channels1020, while also resulting in an interference friction fit bond betweenthe target material 1010 and the backing plate material 1015, is asignificant improvement. The resulting decrease in sputter targetassembly 1005 production time results in reduced cost. In addition, theprotruding portions 1040, when received in receptacles 1096, trap thetarget material 1046 against separation forces, or vectors, that wouldact in shear or in a perpendicular direction relative to the matingsurfaces 1025, 1035. Thereby, a tenacious bond is formed between thetarget material 1010 and the backing plate material 1015 combining thestrengths of the interference friction fit bond and the ZIP bond similarto the fourth embodiment.

Turning now to FIGS. 17 and 18, there is shown a seventh embodiment ofthe sputter target assembly 1205 in accordance with the presentinvention. As best appreciated with reference to FIG. 17, the assembly1205 comprises a target material 1210 and a backing plate material 1215with an interposing material 1211 therebetween. This seventh embodimentis most preferred when the thermal expansion coefficients of the targetmaterial 1210 and the backing plate material 1215 are such that directbonding is impractical. The interposing material 1211 is chosen with athermal expansion coefficient between that of the target material 1210and that of the backing plate material 1215.

Although the seventh embodiment is shown to have a ZIP bond, similar tothe second embodiment, between the target material 1210 and theinterposing material 1211, the bonds as depicted in any of the previousembodiments may be employed; this is similarly true for the bond betweenthe interposing material 1211 and the backing plate material 1215.Additionally, formation of the cooling channels 1420 can, in accordancewith the present invention, result in the channels 1420 being in thetarget material 1210, the interposing material 1211 or the backing platematerial 1215; a second interposing material may also be incorporatedinto the sputter target assembly, this may, within the scope of thepresent invention, result in the cooling channels 1420 being formedwithin an interposing material independent of the remaining componentsof the sputter target assembly 1205.

With further reference to FIG. 17, the protruding portions 1240 areformed as extending from the mating surface 1225 of the interposingmaterial 1211. The grooves 1430 are formed in the mating surface 1435 ofthe interposing material 1211. The grooves 1430 comprise opposingsidewalls 1445, 1450, a bottom portion 1455 and an opening 1460. Eachsidewall 1445, 1450 comprises an upper portion 1465, 1470, respectively,and a lower portions 1475, 1480, respectively. The protruding portions1240 form a substantial “M” shape in cross section and include tips1285, 1290.

A second set of protruding portions 1440 are formed as extending fromthe backing plate material 1215 mating surface 1425 and defining islands1432 therebetween. Each protruding portion 1440 includes opposing sides1485, 1490 and an end portion 1495.

Subsequent to formation of the protruding portions 1240, the grooves1430 and the second set of protruding portions 1440, the mating surface1235 is positioned proximate the mating surface 1225; the mating surface1435 is positioned proximate the mating surface 1425 such that theprotruding portions 1440 align with the grooves 1430.

The sputter target assembly 1205 is then bonded along the annular zones1300, 1500 adjacent the peripheral boundaries 1305, 1505. This initialbonding is preferably performed as with the preceding embodiments. Thisbonding, like all the previous embodiments, may be performed subsequentto the low temperature pressure consolidation described below.

After the peripheral bonding, the sputter target assembly 1205 issubjected to the low temperature pressure consolidation as describedwith regard to the preceding embodiments. The protruding portions 1240penetrate into the target material 1210 and disrupt the oxide film thatmay exist along the mating surface 1235, thereby, promoting a metal tometal cold diffusion type bond. The tips 1285, 1290 deform and fold backtoward the mating surfaces 1225, 1235, providing a physical lockingmechanism, or ZIP bond, between the target material 1210 and theinterposing material 1211.

With further reference to FIG. 18, the deformed edges 1286, 1291 of the“M” shaped protruding portions 240 are bent toward the mating surfaces1225, 1235 as a result of the low temperature pressure consolidation.Each edge 1286, 1291 forms a re-entrant angle of about 55-60° relativeto the mating surfaces 1225, 1235. Due to bending of the edges 1286,1291, the tips 1285, 1290 of the protruding portions 1240 adjacent edges1286, 1291. The ZIP bond traps target material 1246, 1251 againstseparation forces, or vectors, that would act in shear or in aperpendicular direction relative to the mating surfaces 1225, 1235.Thereby, a tenacious bond is formed between the target material 1210 andthe interposing material 1211.

With further reference to FIG. 18, the upper portions 1465, 1470 of thegrooves 1430 cooperate with the sides 1485, 1490 of the protrudingportions 1440 to form a friction fit bond, preferably an interferencefriction fit bond, between the interposing material 1211 and the backingplate material 1215. The lower portions 1475, 1480 and the bottomportion 1455 of the grooves 1430 cooperate with the end portion 1495 ofthe protruding portions 1440 to define the cooling channels 1420.

Having described the above embodiments of the present invention, theartisan will appreciate that many combinations of the individual bondingmethods are within the scope of the present invention. High strengthbonds, required in high rate sputtering processes utilizing sputtertarget assemblies comprising dissimilar target material and backingplate material, are provided by the present invention. The bondingmethods of the present invention are most preferred with sputter targetassemblies incorporating internal cooling channels; the low temperaturepressure consolidation does not induce deformation of the coolingchannels nor cause undesirable grain growth in the target material.

1. A method of manufacturing a sputter target assembly including atarget material with mating surface and a backing plate material withmating surface, comprising: a) forming a plurality of grooves in atleast one of said materials and a plurality of protruding portionsprojecting from at least one of said mating surfaces; b) positioningsaid target material and said backing plate material adjacent each otherto form a sputter target assembly having an interface defined by saidmating surfaces; and c) pressure consolidating said assembly under lowtemperature conditions such that said target material is bonded to saidbacking plate material forming cooling channels therewithin.
 2. A methodof manufacturing a sputter target assembly as in claim 1, wherein saidgrooves are formed in said backing plate material mating surface andsaid protruding portions are formed in said target material matingsurface.
 3. A method of manufacturing a sputter target assembly as inclaim 1, wherein said protruding portions are received within saidgrooves cooperating to form said cooling channels.
 4. A method ofmanufacturing a sputter target assembly as in claim 3, wherein afriction fit bond is produced between said protruding portions and saidgrooves.
 5. A method of manufacturing a sputter target assembly as inclaim 2, wherein said protruding portions are received within saidgrooves cooperating to form said cooling channels.
 6. A method ofmanufacturing a sputter target assembly as in claim 5, wherein afriction fit bond is produced between said protruding portions and saidgrooves.
 7. A method of manufacturing a sputter target assembly as inclaim 1, wherein said protruding portions are “M” shaped in crosssection.
 8. A method of manufacturing a sputter target assembly as inclaim 7, wherein said protruding portions are formed in said backingplate material mating surface.
 9. A method of manufacturing a sputtertarget assembly as in claim 8, wherein said protruding portionspenetrate said target material mating surface producing a ZIP bondbetween said target material and said backing plate material.
 10. Amethod of manufacturing a sputter target assembly as in claim 1, whereinthe protruding portion thickness is greater than the groove width andsaid protruding portions are received within said grooves producing aninterference friction fit bond between said target material and saidbacking plate material.
 11. A method of manufacturing a sputter targetassembly as in claim 1, wherein step b) further comprises; forming aplurality of receptacles in at least one of said mating surfaces.
 12. Amethod of manufacturing a sputter target assembly as in claim 10,wherein said protruding portions are received with said receptaclesproducing a friction fit bond between the target material and thebacking plate material.
 13. A method of manufacturing a sputter targetassembly as in claim 1, wherein said grooves cooperate with one of saidmating surfaces to form cooling channels.
 14. A method of manufacturinga sputter target assembly including a target material with matingsurface, an interposing material with mating surfaces and a backingplate material with mating surface, comprising: a) forming a pluralityof grooves in at least one of said materials and a plurality ofprotruding portions projecting from at least two of said matingsurfaces; b) positioning said target material mating surface adjacent onof said mating surfaces of said interposing material and positioningsaid backing plate material mating surface adjacent said other of saidmating surfaces of said interposing material to form a sputter targetassembly having interfaces defined by said mating surfaces; and c)pressure consolidating said assembly under low temperature conditionssuch that said target material and said backing plate material is bondedto said interposing material forming cooling channels therewithin.
 15. Amethod of manufacturing a sputter target assembly as in claim 13,wherein said grooves are formed in said one of said mating surfaces ofsaid interposing material and said protruding portions are formed in theother of said mating surfaces of said interposing material.
 16. A methodof manufacturing a sputter target assembly as in claim 14, whereinprotruding portions are formed in said backing plate material and arereceived with said grooves producing a friction fit bond between thebacking plate material and the interposing material.
 17. A method ofmanufacturing a sputter target assembly as in claim 15, wherein saidprotruding portions formed in said mating surface of said interposingmaterial penetrate into said target material mating surface producing aZIP bond between said target material and said interposing material. 18.A method of manufacturing a sputter target assembly as in claim 15,wherein cooling channels are formed by cooperation of said protrudingportions with said grooves.
 19. A method of manufacturing a sputtertarget assembly as in claim 13, wherein cooling channels are formed bycooperation of said grooves with one of said mating surfaces.
 20. Methodas recited in claim 1 wherein said target comprises a metal selectedfrom the group consisting of Al, Cu, Ta, W, Ti, and their alloys.